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CivilComp Proceedings
ISSN 17593433 CCP: 89
PROCEEDINGS OF THE SIXTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY Edited by: M. Papadrakakis and B.H.V. Topping
Paper 167
Numerical Simulation of SoilStructureInteraction of Towers and Tanks via Finite and Infinite Elements R. Harte^{1} and E. Mahran^{2}
^{1}Institute for Statics and Dynamics of Structures, University of Wuppertal, Germany
R. Harte, E. Mahran, "Numerical Simulation of SoilStructureInteraction of Towers and Tanks via Finite and Infinite Elements", in M. Papadrakakis, B.H.V. Topping, (Editors), "Proceedings of the Sixth International Conference on Engineering Computational Technology", CivilComp Press, Stirlingshire, UK, Paper 167, 2008. doi:10.4203/ccp.89.167
Keywords: soilstructureinteraction, finiteinfiniteelement modelling, soil halfspace, nonlinear structural behaviour, water tank, cooling tower, monitoring system.
Summary
In order to activate structural reserves to the ultimate load capacity for large concrete
shell structures like cooling towers, a closetoreality description is required, which
considers the typical characteristics of all components  structure and soil, and their
reciprocal effects. Computation models, which modify the structures with idealised
boundary conditions, like spare masses, springs and dampers, are usually not
sufficient and not adequate for the advanced structural model. More comprehensive
analysis models are needed, considering both the geometrical and material
nonlinearity of the concrete structure and its interaction with the supporting soil as
realistic as possible.
A finiteinfiniteelement formulation [1] permits holistic modelling of the structure and soil and its reciprocal static and dynamic interaction. The soil region (halfspace) will be subdivided into a near and a far field. The near field underneath the foundation will be modelled by means of the finite element method and may consider material nonlinearities. The far field will be modelled by means of an infinite element method (finite elements for unbounded domains) and is assumed to behave linearly. The shape function of an infinite element can be characterised by two dominant shape functions: a displacement shape function decreasing in the infinite direction and a geometric shape function increasing in the infinite direction. Whereas the deformation of an infinite element in the infinite direction reaches zero, the geometric position vectors in this direction reach infinity. The threedimensional infinite element considered here possesses only one infinite direction. The geometric shape function results from multiplication of the shape function of the twodimensional finite direction in phi,eta with the geometric shape function of the onedimensional infinite direction in xi according to [2]. The displacement shape function will be composed likewise. These shape functions are valid both for Cartesian and axissymmetric convective coordinate systems and thus will fit perfectly to convective curvilinear shell formulations. In the paper more details are presented and benchmark with verification examples are given for an elastic block under an impulsive loading, a liquid storage tank under earthquake excitation and a cooling tower founded on inhomogeneous inclined halfspace. Furthermore a research and development project is shown, from which significant results for the formulation of holistic structural and geotechnical models are to be expected. Besides the verification of soil models, the extensive monitoring sensorequipment in and underneath a largescale power plant foundation enables a deeper knowledge about the settlement behaviour and its effects on the structure to be received. From these results, features to prevent structural damage may be deduced, but as well conclusions for an economic design of future power plants and of foundations for other largescale and sensitive buildings can be drawn. References
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